1. Field of the Invention
The present invention relates to a semiconductor device having a Cu wiring layer and a method of manufacturing the same.
2. Background Art
With the advance of miniaturization of wiring, Cu, which has a lower resistance, has become more popular as a material of wiring than Al.
And problems have arisen, such as deterioration of the electromigration (EM) resistance because of the miniaturization of wiring and deterioration of the time dependent dielectric breakdown (TDDB) between Cu wiring layers because of using a low dielectric constant film (in particular, a porous low-k film) as an interlayer insulating film.
For example, a conventional method of manufacturing a semiconductor device involves reducing Cu having reacted with oxygen by a plasma processing using a reducing gas (NH3, for example) after planarizing a Cu wiring layer by CMP and before forming a diffusion barrier film (a SiCN film) on the Cu wiring layer. In this way, the EM resistance is improved.
However, according to the method of manufacturing a semiconductor device, a damaged layer is formed on the surface of the low dielectric constant film (in particular, the porous low-k film) because of the plasma processing. And a leak current may flow through the interface between the damaged layer and the diffusion barrier layer formed thereon, thus deteriorating the dielectric strength.
In order to improve the EM resistance, another conventional method of manufacturing a semiconductor device involves selectively depositing CoWP or CoWB on top of a Cu wiring layer (see Japanese Patent Laid-Open Nos. 2006-253666 and 2005-129808, for example). The CoWP or CoWB interposed between the Cu wiring layer and the interlayer insulating film formed thereon can improve the EM resistance.
However, according to the method of manufacturing a semiconductor device intended to improve the EM resistance, after the interlayer insulating film in which Cu wiring is formed, the CoWP or CoWB on the surface of the interlayer insulating film between the Cu wires is removed. However, some of the CoWP or CoWB remains on the surface of the interlayer insulating film between the Cu wires, and the residue may cause a short circuit between the wires.
As described above, the prior art has a problem that it is difficult to improve the withstand voltage of the interface (Cu/SiCN interface) between the Cu wiring layer and the diffusion barrier film and the interface between the low dielectric constant film and the diffusion barrier film (SiCN film).